Biofuels such as bioethanol have been widely used to substitute fossil fuels in the transportation (e.g., gasoline blended with bioethanol) and agricultural sectors. Yet, preparation of fuel-grade ethanol, i.e., anhydrous ethanol, by traditional distillation is an energy intensive process. As a result, significant efforts have been made to explore alternative dehydration techniques that consume less energy.
Pervaporation is known to be energy efficient and to outperform conventional distillation in dehydration of ethanol. The efficiency of membrane-based pervaporation is influenced by membrane materials and the membrane design. In this regard, a hollow fiber is superior to a flat membrane. Recently, the use of a dual-layer hollow fiber for performing pervaporation has gained wide acceptance. Typically, a dual-layer hollow fiber is prepared by a spinning technology that requires different polymer materials for the two layers. To reduce cost, the outer layer, serving as a selective layer, is made of a high performance material, whereas the inner layer, serving as a support layer, is fabricated from an inexpensive material. As the outer layer is unshielded, its swelling reduces pervaporation efficiency.
The need exists to obtain high-performance hollow fibers for use in dehydration of ethanol and other organic solvents via a pervaporation process.